Methods of Installing Nails or Reinforcements in Soil Nailing Walls

In the United States, soil nails (or reinforcements) are predominantly installed using the drill-and-grout method. However, several other installation techniques are also commonly employed.

Soil Nailing Installation Techniques

The main types of soil nail (reinforcement) installation methods are categorized as follows:

Drill-and-Grout Nails

Boreholes with diameters between 100 and 200 mm are drilled into the foundation soil at approximately 1.5-meter spacing. Steel bars are then placed inside the holes and grouted.

Drill-and-grout nails represent the most common soil nailing system used for stabilized walls, applicable for both temporary and permanent structures (provided proper corrosion protection systems are in place).

Displacement (Driven) Nails

These nails have relatively small diameters, typically 19 to 25 mm, and are driven directly into the soil by force.

They are spaced approximately 1 to 1.5 meters apart.

Driven nails install faster than drill-and-grout nails but usually lack adequate corrosion protection, regardless of bar thickness, making them suitable mainly for temporary stabilization walls.

Self-Drilling Nails

Hollow steel bars are used to perform drilling and grouting simultaneously. While drilling, grout is injected through the hollow bar, filling the borehole from top to bottom.

This method uses rotary-percussion drilling techniques and installs faster than drill-and-grout nails. Unlike driven nails, self-drilling nails benefit from partial corrosion protection provided by the grout.

This system is the most common for temporary stabilization walls.

Jet-Grouted Nails

This technique employs high-pressure grout injection to drill and advance the borehole to the target depth.

The grout provides corrosion protection for the steel bars.

Subsequently, steel bars are installed, typically using percussion-vibration drilling methods.

Launched (Projectile) Nails

Bare steel bars (without coating) are propelled into the soil at very high velocities using compressed air.

These bars generally have diameters of 19 to 25 mm and lengths of about 8 meters.

This technique allows rapid installation with minimal disturbance to the surrounding environment but may make controlling penetration depth challenging.

Launched nails are mainly used for temporary stabilization.